Screen printing requires addressing some simple issues. Cleaning the screen is one such easily manageable problem, yet many operators perform it poorly, resulting in waste, affecting print quality, and shortening the lifespan of the template.
When there is dirt or dried ink on the graphic printing area, the screen should be cleaned. After stopping the printing machine, lift the frame, at which point some operators may vigorously rub the bottom of the template with solvent-soaked sandpaper, the noise of which can be heard throughout the printing workshop. This often leads to damage to the template.
A knowledgeable operator wouldn't vigorously rub the graphic printing surface of a template, as they know that the clarity of the printed graphics requires all graphic edges to maintain a clear emulsion layer interface. Aggressive rubbing can damage the emulsion layer interface, even removing the emulsion layer, leaving only bare mesh.
When printing high-resolution color images, the emulsifying film beneath the silk is only 5-6μm thick, and the diameter of the mesh's silk may only be 30μm, which cannot withstand vigorous rubbing. Therefore, the key to avoiding rough cleaning is to first prevent the template from being contaminated.
The primary cause of stencil contamination is improper ink control, leading to dried ink remaining in the mesh. When using solvent-based or water-based inks, the issue arises from the ink being too thin or too thick. It is essential to mix additives according to the specified quantities during ink mixing. Additionally, it is advisable to add small amounts of pre-mixed ink regularly during the printing process to maintain the ink's consistency. When using UV-curing inks, efforts should be made to avoid exposing the stencil to UV light from lamps and sunlight.
Another ink control issue is related to improper speed adjustment of the printing press. Incorrect automatic or manual operation of the press speed can lead to uneven ink supply, causing the mesh with insufficient ink to dry quickly.
A common cause of ink drying is improper adjustment or wear of the blade. When printing fine images with high-line screen, a blade with a very sharp edge is required, at an angle of approximately 75 degrees. As the blade may deform or wear during normal use, the clarity of the surrounding images will decrease, indicating that the ink may not pass through the screens properly. If this issue is not addressed promptly, the ink can solidify within the screens. To avoid such problems, the blade should be flipped regularly to extend its blade edge life, or a new blade should be used before the print quality degrades.
To ensure the mesh functions properly, it is essential to clean any dirt from within the inks or on the printing substrate. Contaminants may adhere to the substrate surface due to static attraction of airborne particles and poor storage conditions. These issues can be resolved by improving storage conditions and process control. Additionally, using static eliminators and substrate cleaning devices can prevent dust and dirt from transferring from the substrate surface to the mesh.
How to handle contamination of the template? When using the screen printing machine on the platform, stop the machine after printing a set of sheets, then insert a sponge paper to make the screen contact with the sponge paper.
Position the silk screen over the printing area, then use a non-abrasive soft cloth dipped in silk screen cleaner to wipe away dirt from the squeegee surface. Avoid excessive force to ensure dirt falls through the mesh onto the absorbent paper below. Repeat with another absorbent paper if necessary. Larger dirt particles that may not pass through the mesh can be picked up with a soft cloth. Once cleaned, dry the stencil with a hairdryer set to "cold air."
      When cleaning a round screen printing machine, various situations may arise. Due to the design structure, it's not possible to simply wash away dirt onto absorbent paper like with a standard screen printing machine. Fortunately, because of the fast printing speed, it's unlikely that ink will dry in the mesh holes. If this occurs, first stop the machine after completing a set of prints, then apply a non-abrasive soft cloth soaked in screen cleaner or thinner to the top of the template at the printing graphic area. Be cautious not to leave too much cleaner on the template top. The goal at this point is to brush away dirt inside the mesh holes with the solvent.